Wow- nice study!! Do studies of the old masters help you a lot? I used to emulate drawings I admired when I was younger, but recently I found that I advance my skills far faster by studying natural objects. Maybe the reason for that was that I didn't understand how the artists had created their finished drawings, and the steps and careful study that went into it. I could not learn those skills just by seeing the finished artwork any more than I could learn to weave a basket by looking at a finished basket- thus, it was onward to the basics for me!
It's more to do with understanding their style. By looking closely at a painting you can gradually start to see how it's put together - how they paint skin, the tones they use to compliment each other, the way they paint trees etc. It's really something you do after getting the hang of foundation principles though, perspective, proportion etc.